The present invention relates to thin film transition metal chalcogenides and in particular to a chemical spray deposition process employed in conjunction with a thermal ion exchange process for producing metal and mixed metal chalcogenides.
Thin film technology plays numerous and increasingly important roles in solar energy conversion. Materials in thin film form are utilized in solar photovoltaic applications, such as cadmium sulfide-copper sulfide solar cells. Thin film materials are also utilized to provide efficient solar energy absorbers for solar thermal energy conversion systems. Thin film technology offers significant reductions in the amounts of raw materials necessary to fabricate these devices. Thin film solar energy devices are acclaimed by those in the art to be the most promising of the numerous solar energy devices. Conventionally, these films are produced by high vacuum process such as thermal evaporation and sputtering. These conventional techniques are prohibitively expensive for large area thin film applications. The cost of producing large area thin films by these methods has been a principal impediment in the development of solar energy as a viable alternative to present energy producing means.
An alternative film growth process is chemical spray deposition. Spray deposition is an inherently simple process requiring only a substrate heater and an atomizer. Spray deposition has been shown to be an efficient and economical means for large area thin film depositions. Chemical spray deposition has been demonstrated in diverse applications such as producing tin oxide or cadmium sulfide for example. Film growth is limited only by the requirement that the solution species decompose at the substrate to give the desired film. Deposition rates and film content are readily controlled by the degree of atomization and the solution content. Intentional film dopants, variant doping profiles, and other similar depositions specialties, available only in very complex vacuum deposition systems, are readily achieved by spray deposition. Furthermore, these parameters are achieved at a substantial cost savings over conventional vacuum techniques.
The present invention teaches a method for chemically spray depositing an oxide film of a metal or mixed metal. The oxide film is then heat treated in the presence of a chalcogen gas to produce a chalcogenide film useful in solar energy conversion devices.